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Biomedical subjects

J L Morgan

Publications and source records attributed to J L Morgan.

At least 19 recordsLinked to original sources
PubMed1999

Phonotactic and prosodic effects on word segmentation in infants.

This research examines the issue of speech segmentation in 9-month-old infants. Two cues known to carry probabilistic information about word boundaries were investigated: Phonotactic regularity and prosodic pattern. The stimuli used in four head turn preference experiments were bisyllabic CVC.CVC nonwords bearing primary stress in either the first or the second syllable (strong/weak vs. weak/strong). Stimuli also differed with respect to the phonotactic nature of their cross-syllabic C.C cluster. Clusters had either a low probability of occurring at a word juncture in fluent speech and a high probability of occurring inside of words ("within-word" clusters) or a high probability of occurring at a word juncture and a low probability of occurring inside of words ("between-word" clusters). Our results show that (1) 9-month-olds are sensitive to how phonotactic sequences typically align with word boundaries, (2) altering the stress pattern of the stimuli reverses infants' preference for phonotactic cluster types, (3) the prosodic cue to segmentation is more strongly relied upon than the phonotactic cue, and (4) a preference for high-probability between-word phonotactic sequences can be obtained either by placing stress on the second syllable of the stimuli or by inserting a pause between syllables. The implications of these results are discussed in light of an integrated multiple-cue approach to speech segmentation in infancy.

Female↗
PubMed1998

Phonological and acoustic bases for earliest grammatical category assignment: a cross-linguistic perspective.

Maternal infant-directed speech in Mandarin Chinese and Turkish (two mother-child dyads each; ages of children between 0;11 and 1;8) was examined to see if cues exist in input that might assist infants' assignment of words to lexical and functional item categories. Distributional, phonological, and acoustic measures were analysed. In each language, lexical and functional items (i.e. syllabic morphemes) differed significantly on numerous measures. Despite differences in mean values between categories, distributions of values typically displayed substantial overlap. However, simulations with self-organizing neural networks supported the conclusion that although individual dimensions had low cue validity, in each language multidimensional constellations of presyntactic cues are sufficient to guide assignment of words to rudimentary grammatical categories.

China↗
PubMed1997

Determination of testis temperature rhythms and effects of constant light on testicular function in the domestic fowl (Gallus domesticus).

There is a wide range of opinions regarding the operating temperature of the testis in the domestic fowl. We used physiological monitoring techniques to investigate testis and body temperature over daily periods and under various light regimes to elucidate body temperature gradients in the fowl. We confirm that the operating temperature of the adult fowl's testes is equivalent to core body temperature (40-41 degrees C). Long-term continuous temperature monitoring showed that there was no difference between the temperature of the testis, liver, and peritoneum during a 24-h period either in a normal light:dark cycle or under constant light conditions. However, there was a slight decrease in all temperatures at subjective night in each case, a decrease that does not appear to be sufficient to influence spermatogenesis. Birds maintained under constant light throughout two cycles of the seminiferous epithelium (28 days) still exhibited normal testis function and structure, even when "nightly" testis temperature decrease was the lowest. Thus, by undergoing spermatogenesis at an elevated temperature, the domestic fowl system is unique among the homeothermic animal systems studied to date.

Animals↗
PubMed1996

Osteoid osteoma and osteoblastoma: MRI appearances and the significance of ring enhancement.

We assessed the value of contrast-enhanced fat-suppressed MRI on nine patients with osteoid osteomas and osteoblastomas. The results were compared with plain films, bone scintigraphy, computed tomography (CT) and pathological specimens. On contrast-enhanced fat-suppressed T1-weighted images the non-calcified nidi showed homogeneous enhancement, whereas the calcified lesions showed a ring enhancement sign that was proportional in intensity to the extent of the remaining part of the vascularized nidus. The degree of bone marrow and soft tissue enhancement was relative to the size and reactive inflammatory changes of the lesions. Although CT was diagnostic in most of the cases and more specific to show the calcified lesions, MRI was confirmatory in one case. We concluded that, although CT is the primary diagnostic investigation in osteoid osteomas, MRI can be reserved for equivocal cases.

Adolescent↗
PubMed1995

Expression pattern and mapping of the murine versican gene (Cspg2) to chromosome 13.

Versican is a modular proteoglycan harboring a hyaluronan-binding domain at its amino-terminal end and a selectin-like domain at its carboxyl-terminal end, separated by a large intervening region containing the attachment sites for the glycosaminoglycan side chains. By virtue of its modular nature, versican may play a role in cellular attachment, migration, and proliferation by interacting with cell surfaces and extracellular matrix molecules. To discern the function of versican through the analysis of spontaneous and targeted genetic mutations, we have isolated a mouse versican cDNA encoding part of the hyaluronan-binding region, analyzed its mRNA expression in various adult mouse tissues and embryos, and determined the chromosomal location of the gene. Murine versican was 89% identical to human versican at the amino acid level and was highly expressed in mouse embryos at Days 13, 14, and 18. Expression was also detected in adult mouse brain, heart, lung, spleen, skeletal muscle, skin, tail, kidney, and testis. Using interspecific backcross analysis, we assigned the versican gene (Cspg2) to mouse chromosome 13, in a region that is syntenic with the long arm of human chromosome 5 where the human CSPG2 gene is located.

3T3 Cells↗
PubMed1995

Insulin signaling in chick embryos exposed to alcohol.

Although insulin is known to be an important generator of regulatory signals during fetal growth and development, neither the immediate nor long-term effects of alcohol (ethanol) on insulin action are well understood. In the rat, fetal exposure to alcohol has been shown to be correlated with a subsequent abnormal response to a glucose load in the neonate and adult. Further, fetal hypoplasia secondary to maternal alcohol consumption is correlated with decreased placental glucose transport and with a lowering of the glucose levels in fetal tissues. However, the fetal effects of alcohol cannot be completely overcome by glucose/caloric supplementation, suggesting that factors other than glucose transport are involved. Using an embryonic chick model that negates the factors of maternal/placental metabolism and transport, the current study found that fetal alcohol exposure markedly increased insulin binding in developing tissue, but had little effect on the binding of the insulin-like growth factors. Competitive binding experiments revealed a marked increase in insulin receptor numbers, but no change in binding affinity as a result of the alcohol exposure. Basal uptake of 2-deoxyglucose by fetal tissue was lowered by alcohol exposure, but incubation with exogenous porcine insulin (1 x 10(-7) M) resulted in a significant increase in glucose uptake by the alcohol-exposed embryos. The increases in insulin binding and in insulin-dependent glucose uptake notwithstanding, exogenous insulin could not induce normal levels of ornithine decarboxylase activity in embryonic cells previously exposed to alcohol.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Role of CT and MR imaging in the management of tuberculous spondylitis.

Tuberculous spondylitis is an infection involving one or more of the components of the spine, namely the vertebral body, intervertebral disc and ligaments, paravertebral soft tissues, and the epidural space. The causative organism belongs to one of the different strains of Mycobacterium tuberculosis. The role of CT and MR imaging in the diagnosis and management of tuberculous spondylitis is reviewed, and the differential diagnosis of these appearances is discussed. The possible impact of HIV infection on the number of reported cases and their mode of presentation also is considered. The need for prompt diagnosis is emphasized.

AIDS-Related Opportunistic Infections↗
PubMed1995

Emerging integration of sequential and suprasegmental information in preverbal speech segmentation.

5 studies examined contributions of syllable-ordering and rhythmic properties of syllable strings to 6- and 9-month-old infants' speech segmentation. A pair of methods measuring complementary properties of representational units was used: a noise detection task sensitive to perceived cohesiveness of pairs of syllables, and a discrimination maintenance task sensitive to compactness of representations of syllable pairs. For 9-month-olds, results show that a key pair of syllables was represented as a unit when the grouping of these syllables was supported by correlated regularities of ordering and rhythm in the set of stimulus strings, but not when such grouping was supported by only rhythmic or only syllable-ordering regularity. For 6-month-olds, results show that a key pair of syllables was represented as a unit whenever grouping was supported by rhythmic regularity in the stimulus strings, regardless of whether syllable-ordering regularity was also present. Thus, whereas 9-month-olds appear to be capable of integrating sequential and suprasegmental information in forming worldlike (multisyllabic) phonological percepts, 6-month-olds are not. The emergence of integrative abilities portends increased efficiency in speech processing and may contribute to the formation and use of an initial lexicon.

Child Language↗
PubMed1994

The murine decorin. Complete cDNA cloning, genomic organization, chromosomal assignment, and expression during organogenesis and tissue differentiation.

Decorin, a proteoglycan known to interact with collagen and growth factors, may play key roles during ontogenesis, tissue remodeling, and cancer. We have deciphered the complete protein sequence of the murine decorin by cDNA cloning, elucidated its gene structure and chromosomal location, and investigated its expression in the developing embryo. The decorin protein and the gene were highly conserved vis à vis the human counterpart; however, the murine gene lacked a leader exon, exon Ib, which was found only in the human. Using interspecific backcrossing, we assigned the gene to chromosome 10 just proximally to the Steel gene locus. In situ hybridization studies of developing mouse embryos showed a distinct pattern of expression with a progressive increase of decorin mRNA during ontogenesis. At early stages (day 11 postconception), decorin was detectable only in the floor plate region. Subsequently (days 13-16 postconception), decorin expression was especially prominent in the meninges and mesothelial linings of pericardium, pleura, and coelomic cavity, as well as in the dermis and subepithelial layers of the intestine and urinary bladder. In contrast, the major parenchymal organs were only weakly positive for decorin mRNA. These findings suggest that decorin may play a role in epithelial/mesenchymal interactions during organ development and shaping.

3T3 Cells↗
PubMed1993

Quantitation of cytokine levels in skin graft donor site wound fluid.

We quantified endogenous levels of multiple cytokines in skin graft donor site wounds in patients with small to moderate-sized burn injuries. Thirteen patients aged 11 months to 61 years with mean TBSA burn of 4 +/- 1 per cent underwent placement of occlusive wound dressings on partial skin thickness donor site wounds. Fluid was aspirated from beneath the dressing on postoperative day 1 and every subsequent 24 h until no further fluid could be obtained. Interleukin-1 alpha (IL-1) and tumour necrosis factor-alpha (TNF-alpha) levels were determined by enzyme-linked immunosorbent assay (ELISA). Epidermal growth factor (EGF), basic-fibroblast growth factor (bFGF), and platelet-derived growth factor (PDGF) were measured by an enzyme immunoassay (EIA). We found substantial levels of EGF and TNF-alpha in the donor site wound fluid in all 13 patients; detectable levels of bFGF in five patients; and elevated levels of IL-1 in three patients. There were no detectable levels of these cytokines in normal human serum. In contrast, there were no measurable levels of PDGF in any patient's wound fluid; the mean level in serum was 1.5 ng/ml +/- 0.2 s.e.m. Studies of cytokines in the normal wound healing environment may help in the design of future therapies to augment wound healing.

Adolescent↗
PubMed1993

Perceptual strategies in prelingual speech segmentation.

Previous work has suggested that infants may segment continuous speech by a BRACKETING STRATEGY that segregates portions of the speech stream based on prosodic cues to their endpoints. The two present studies were designed to assess whether infants also can deploy a CLUSTERING STRATEGY that exploits asymmetries in transitional probabilities between successive elements, aggregating elements with high transitional probabilities and identifying points of low transitional probabilities as boundaries between units. These studies examined effects of the structure and redundancy of speech context on infants' discrimination of two target syllables using an operant head-turning procedure. After discrimination training on the target syllables in isolation, discrimination maintenance was tested when the target syllables were embedded in one of three contexts. Invariant Order contexts were structured to promote clustering, whereas the Redundant and Variable Order contexts were not. Thirty-six seven-month-olds were tested in Experiment I, in which stimuli were produced with varying intonation contours; 36 eight-month-olds were tested in Experiment 2, in which stimuli were produced with comparable flat pitch contours. In both experiments, performance of the three groups was equivalent in an initial 20-trial test. However, in a second 20-trial test, significant improvements in performance were shown by infants in the Invariant Order condition. No such gains were shown by infants in the other two conditions. These studies suggest that clustering may complement bracketing in infants' discovery of units of language.

Acoustic Stimulation↗
PubMed1990

Input, innateness, and induction in language acquisition.

Input and innateness compliment one another in language acquisition. Children exposed to different languages acquire different languages. Children's language experience, however, underdetermines the grammars that they acquire; the constraints that are not supplied by input must be available endogenously, and the ultimate origin of these endogenous contributions to acquisition may be traced to the biology of the mind. To the extent that assumptions of innateness encourage greater explicitness in the formulation of theories of acquisition, they should be welcomed. Excessively powerful assumptions of innateness may not be subject to empirical disconfirmation, however. Therefore, attention should be devoted to the development of a theory of language input, particularly with regard to identifying invariants of input. In combination with a linguistic theory providing an account of the endstate of acquisition, a theory of input would permit the deduction of properties of the mind that underlie the acquisition of language.

Child Language↗
PubMed1990

Imitation of intonation by infants.

Children between 9 and 12 months of age were studied to determine if they would spontaneously imitate either the average fundamental frequency or the fundamental frequency contour of their speaking partners. In the first experiment, children were recorded at home as they interacted with their fathers and mothers. Acoustic analyses failed to reveal any tendency on the part of the infants to adjust vocal pitch, amplitude, or duration to those of their speaking partners. In a second experiment, children were recorded while interacting with their parents in a laboratory setting. Again, there were no indications that the children imitated the vocal patterns of their speaking partners.

Conditioning, Psychological↗